A Grinding Circuit is a key section of a mineral processing plant in which ore, after primary crushing, is further reduced in particle size through mechanical comminution to liberate valuable minerals from the host rock matrix and prepare the material for subsequent beneficiation processes such as flotation, leaching, gravity separation, or magnetic separation. The grinding circuit typically consists of one or more mills — including Semi-Autogenous Grinding (SAG) mills, Autogenous Grinding (AG) mills, ball mills, rod mills, or vertical stirred mills — operated in open or closed circuit with classification equipment such as hydrocyclones or screens.
In gold processing, the grinding circuit reduces ore to a fine particle size, often below 75 micrometres (200 mesh), to maximise gold exposure to cyanide leaching solutions. In iron ore processing, grinding is used to liberate iron minerals from silica for subsequent magnetic separation or flotation. In bauxite processing through the Bayer process, bauxite is ground to a fine slurry before digestion in hot caustic soda solution.
In diamond processing, grinding is deliberately avoided in primary circuits to prevent diamond breakage, with crushing and scrubbing preferred instead. The efficiency and energy consumption of the grinding circuit are major determinants of overall processing plant operating costs, as grinding is the most energy-intensive step in mineral processing. Circuit design involves balancing throughput, particle size targets, energy consumption, and media wear rates.